Method of providing roadways with a nonskid surface and product thereof



Sept. 25, 1934. E, c. WALLACE METHOD'OF PROVIDING ROADWAYS WITH ANONSKID SURFACE AND PRODUCT THEREOF Filed April 18, 1933 2 Sheets-Sheet1 OLD CONCRETE W11H-' DEPRESSION-S FILLED Fig.2

/NVENTOR-' (310M 8w Alla-ATTORNEY Sept. 25, 1934. 5 Q7 WALLACE I1,975,028

METHOD OF PROVIDING ROADWAYS WITH A NONSKID SURFACE AND PRODUCT THEREOFFiled ,April 18, 1935 2 Sheets-Sheet 2 'GRANULAR Nag-52m: SURFACEATTORNEY Patented Sept. 25, 1934 METHOD OF PROVIDING ROADWAYS WITH ANONSKID SURFACE AND THEREOF PRODUCT Edwin C. Wallace, Newton, Mass.

Application April 18, 1933, Serial No. 666,721

This invention relates to a method of providing roadways with a non-skidsurface and product thereof, and has particularly to do with abituminous paving structure adapted to prevent or minimize skidding. Theinvention finds its chief use in resurfacing or the provision of anadditional surface upon existing worn or defective pavements, though itis also adapted to be used for wholly new construction.

The change in trafiic conditions which has occurred since the advent ofrapidly moving motor vehicles, as compared with slow moving steeltiredvehicles, has created a demand for a riding surface upon which the motorvehicles will not 5 slip or skid as upon the smooth surfaced roads andstreets so long in general use.

Heretofore efforts have been made to provide a non-skid surface byscattering over pavements of the sheet asphalt type or other smoothsurface pavements, stone chips, coarse sand, gravel or the like toprovide a gritty surface. Such efforts have proven to be but temporaryexpedients which within a short time, usually but a few weeks, werecompletely dissipated through various causes, largely due to the factthat the stone chips were either displaced by traffic or else became socompletely embedded in the underlying surface that the non-skidcharacteristic was entirely lost.

. The herein described construction has for its object the provision ofa non-skid pavement which will maintain the integrity of its structureand surface and also maintain the desired nonskid properties of thesurface for a long period of time.- Briefly, this improvement consistsof a relatively thin, non-skid layer or course, comprising two separateand distinct bituminous mixtures which have entirely different physicalproperties and which are combined into a single unitary layer in suchmanner as to utilize to the full the desirable characteristics of eachmixture. This layer may be built upon any existing pavement of anydesired type as a resurfacing or reconstruction measure, or it may .beused in connection with a new under or body layer to form a wholly newpavement with the non-skid feature built directly into the newstructure.

In the drawings:

Fig. 1 is a perspective view illustrating a section of an old, concretepavement to be resurfaced;

Fig. 2 is a plan view of the same after the chief depressions have beenfilled;

Fig. 3 is a perspective view (in substantially actual size) of thecompleted resurfaced section showing to good advantage the coarse,granular texture of the surface; and

Fig. 4 is an additional perspective view (in reduced size) showing asomewhat larger portion of the completed pavement.

(Cl. Sid-23) When applied to an existing pavement or roadway the firststep is to correct the contour of the old pavement by fillingdepressions, removing high spots and strengthening all weak places.

Referring to Figs. 1 and 2 of the drawings,- Fig. 1 illustrates rough,worn concrete and Fig. 2 shows the same after the chief depressions havebeen filled by the deposit therein of any suitable material, forexample, a bituminous concrete mixture, though such depressions may befilled simply by the composition of bituminous cement and fine mineralmatter as hereinafter described.

Following such preparatory work, the preferred procedure is asfollows,the surface is then cleaned in any suitable manner and given acoat of adhesive, bituminous paint. After the paint has become tacky,there is spread over it to the approximate depth of loose measurement(30-50# per sq. yd.) a composition of bituminous cement and fine mineralmatter of such nature that it will readily conform to the old surface,be compressed into shallow depressions and be brought into close contactwith and thoroughly united to the old surface,thus to serve as a bondingcontacting element into which the coarse particles of the granular,non-skid layer may be partially embedded, as best shown in Fig. 3. As anexample of mixture suitable for this purpose, the following is given:

Percent Bitumen 3-13 Passing 8 mesh 55-85 Passing mesh 15-35 Immediatelyafter this fine mixture is spread, it is lightly compressed to bring itinto contact with the underlying surface but not sufficient to preventits uniting with the granular mixture which is applied over it.

The lightly compressed fine mixture may then be straight-edged to ensuregood contour and then covered with a granular surface mixture of suchnature and to such depth that when compressed into a firmly coherentmass, the two mixtures are combined into a single layer, the uppersurface of which presents an open, granular texture with relativelylarge interstices between the particles. A

As an example of mixture suitable for the It will be noted that' thisexample of the pre= ferred granular surface mixture includes a sub=stantial percentage of fines. I have discovered that this is a factor ofimportance for it increases materially both the structural strength ofthe surface and the bond of the granular particles to each other and tothe underlying holding medium or contact layer.

This layer is spread to an approximate depth of loose measurement (35 toper sq. yd.) Immediately after spreading, compression should be appliedby means of a heavy roller. The rolling should be'continued until themass becomes unyielding. Figs. 3 and 4 show the completed construction.

While designed primarily as a renewal or reconstruction measure, whenadopted as newsconstruction, the procedure would be similar to thatoutlined above, except that a new body layer would be substituted forthe old pavement and therefore the cleaning, painting, etc. isunnecessary. Preferably the new body layer consists of acoarse-aggregate bituminous composition, well graded from coarse to fineso as to produce low voids and form a dense, stable layer when properlyconsolidated. This layer which, for convenience, has been called thebody layer, should be supported upon a previously prepared foundation ofadequate strength.

While the body layer may be of any desired depth, it is usually spreadto a depth approxi-,

mating 2" loose measurement.

After light compression the surface is straightedged then covered with athin layer of fine mixture as described above, which in turn is lightlycompressed, straight-edged and then covered with granular surfacemixture as described and the entire mass then thoroughly consolidated bymeans of a heavy roller.

The compression and straight-edging applied to the body layer and theintermediate layer of fine mixture may be omitted if desired, but betterresults are obtained by compression as described.

By this method there is produced a riding surface of desirable roughtexture which is held firmly in place by the fine mixture, the latterforming a holding medium into which the coarse particles are partiallybut firmly embedded.

To'preserve the granular texture it is important that the fine mixturebe spread to sufiicient depth to" act as a conforming and contactingmeans between the granular surface mixture and the underlying supportinglayers, so as to bond them firmly together by forming a holding mediuminto which the coarse particles may be partially embedded, but not socompletely as to cause the 'niixtureto flush up and destroy the granulartexture of the surface.

The-depth of the conforming contact layer is controlled by the averagesize of the coarse particles composing the granular surface mixture. Forinstance, withgranular surface mixture composed largely of A" particlesthe conforming contact layer should have an approximate depth of to ofan inch. When, however, the granular surface mixture is composed largelyof particles, the conforming contact layer (and the granular mixture aswell) should have a depth approximating to loose measurement. It ispreferable, especially in reconstruction work where the underlying bodylayer is hard, that the stone particles of the granular surface bespaced or cushioned from saidhard body layer.

Similarly, when the body layer consists of a new but hardened layer ofmaterial. Where, however, the intermediate layer is laid upon a bodylayer while the latter is still plastic, it is of little importancewhether the granular particles be vertically spaced from the body layer.When larger sized particles are used, the depth of the contact layershould be increased in proportion.

In this construction the fine mixture serves the dual purpose of (a)Conforming and contacting layer which will readily conform to slightinequalities in the old surface and thus serve as a perfect contactmeans between it and the more rigid granular layer which could notconform to slight irregularities.

(b) It also serves as a holding medium into which the coarse particlesare partially em-' bedded thus reinforcing the granular layer andgreatly increasing the resistance to displacement.

By this method the contact and granular layers become, in effect, asingle unified layer having at the bottom bonding and cushioningcharacteristics and at the top the highly desirable and eflicientnon-skid granular wearing surface.

The granular mixture prepared with or mesh particles appears mostsatisfactory for all general purposes for when the mixture is made of $4particles the texture of the surface is rather too fine to beeffectively non-skid. 0n the other hand, however, with particles of 1"and larger in size, the number of points of contact between theparticles as well as the number of particles in a given area are soreduced as to cause poor distribution of the weight of loaded vehiclespassing over the surface, with the consequent result that individualparticles are frequently over-stressed and either shattered under theweight of the load or become dislodged by traflic.

I am aware that it has been the practice for years to clean and paintthe surface of an old pavement and then to apply thereover freshbituminous mixture to rebuild the surface and 115 correct inequalities.I am not aware, however, that it has been the practice to follow the procedure described in this application, namely apply a relatively finebituminous mixture to serve as a conforming contact layer and also toform a 120 holding medium into which a coarser granular surface layer asdescribed may be partiallyembedded to provide a firmly held, coarsegranular textured surface which does not fiush up and become smoothunder trafilc. Le

Having described my invention what I claim is:

1. The method of renewing pavement surfaces which consists in correctingthe contour of the surface, cleaning and applying thereto an adhesivebonding paint, then spreading thereover andcompressing into intimateconnection therewith a conforming and contacting medium of relativelyfine mineral matter and bituminous cement, and then spreading over saidmedium and partially embedding therein a. relatively 135 coarsecomposition of mineral matter and bituminous cement to provide a coarsetextured granular surface with relatively large interstices between theparticles.

2. The method of renewing old pavement sur- 140 faces which consists infilling the depressions therein, cleaning and applying to the oldsurface an adhesive paint, then applying thereover to a depth of onequarter inch or more a plastic, conforming and contacting mixture ofrelatively fine mineral matter and bituminous cement and compressing itinto intimate relation with the old surface, and then spreadingthereover an open, coarse to fine composition of mineral matter andbituminous cement and consolidating the mass to provide a coarsetextured granular surface with relatively large interstices between theparticles.

3. The method of reconditioning old pavement surfaces which comprisescorrecting the contour, cleaning, painting with adhesive paint, thenapplying a close textured conforming and contacting layer consisting offine granular mineral matter coated with bituminous cement, thencovering it with a layer of granular coarse textured composition ofmineral matter coated with bituminous cement and compressing the mass topartially embed the coarse particles of the granular mixture into thefine, close textured conforming and contacting layer to provide a coarsetextured granular surface with relatively large interstices between theparticles.

4. The method of reconditioning old pavement surfaces which comprisescorrecting the contour of the old surface and spreading thereover to adepth of one quarter inch or more a plastic mixture of fine mineralparticles coated with bituminous cement to provide a close texturedconforming and contacting layer, bringing said mixture into intimateconnection with the old surface by compression, then spreading thereoverand partially embedding therein a relatively coarse textured granularcomposition of coarse mineral particles coated with bituminous cement toprovide a coarse textured granular surface with relatively largeinterstices between the particles.

5. A pavement comprising a granular coarse textured surface layerconsisting of coarse mineral particles and fine mineral particles, allcoated with bituminous cement, reinforced and stabilized by beingembedded in a fine textured, plastic composition of mineral matter andbituminous cement to such an extent only that the upper portion of thelayer remains open and granular.

6. A pavement comprising a granular, coarse textured surface layerconsisting of coarse mineral particles and fine mineral particles, allcoated with bituminous cement, reinforced and stabilized by beingembedded .in a fine textured plastic composition of mineral matter andbituminous cement to not substantially more than A of the depth of thecoarse particles.

7. In a pavement, a unified layer of dissimilar bituminous pavingmixtures with a comparatively rigid, coarse textured, anti-slip uppersurface and a plastic, close textured lower surface which conforms toand contacts with a supporting layer to which it is united by means ofan adhesive paint coat.

8. A non-skid paving structure having a body layer, 'an intermediatelayer of fine plastic mixture consisting essentially of bitumen and afine mesh aggregate, and a surface layer of mediumcoarse bituminous-mixture consisting principally of stone larger than the mineralparticles in said intermediate layer all coated with bituminous cementand providing a wearing surface of open granular texture with relativelylarge interstices between the stone of said layer, said intermediatelayer of fine plastic mixture providing a holding medium in which therelatively coarse particles of the granular surface layer arebutpartially embedded.

9. A non-skid paving structure having a body layer, an intermediatelayer of fine plastic mixture consisting essentially of bitumen and afine mesh aggregate, and a surface layer of mediumcoarse bituminousmixture consisting principally of stone larger than the mineralparticles in said intermediate layer all coated with bituminous cementand providing a wearing surface of open granular texture with relativelylarge interstices between the stone of said layer, said intermediatelayer of fine plastic mixture providing a holding medium into which therelatively coarse particles of the granular surface layer extend butpartially and are there firmly held but spaced from said body layer.

10. A non-skid paving structure having a body layer with a coating ofasphaltic paint adherent thereto, an intermediate layer of fine plasticmixture consisting essentially of fine mesh aggregate coated withbituminous cement, and a surface layer of medium-coarse bituminousmixture consisting principally of substantially uniform size stonelarger than the mineral particles in said intermediate layer as well asa small proportion of fines all coated with bituminous cement thusproviding a wearing surface of open granular texture with relativelylarge interstices between the stone of said layer, said intermediatelayer of fine plastic mixture providing a holding medium in which therelatively coarse particles of the granular surface layer are butpartially embedded.

11. A non-skid paving structure having as a body layer an old pavement,a coating of asphaltic paint adherent thereto, an intermediate layer offine plastic mixture consisting essentially of fine mesh aggregatecoated with bituminous cement, and a surface layer of medium-coarsebituminous mixture consisting principally of mineral particles largerthan the stone in said intermediate layer coated with bituminous cementthus providing a wearing surface of open granular texture withrelatively large interstices between the stoneof said layer, saidintermediate layer of fine plastic mixture providing a holding medium inwhich the relatively coarse particles of the granular surface layer arebut partially embedded.

EDWIN C. WALLACE.

